Abstract: "In finite dimensional differential geometry their are close connections between spherical buildings, symmetric spaces, isoparametric submanifolds and polar actions. For example there is a 1:1 correspondance between poinspherical building. For a generalization of this situation to infinite dimensions one has to construct completions of the building corresponding to various functional analytic function spaces. We call those completions universal geometric twin buildings. In this talk we investigate the finite dimensional theory and its generalization to the infinite dimensional situation."